CIESC Journal ›› 2019, Vol. 70 ›› Issue (7): 2540-2547.DOI: 10.11949/0438-1157.20190065

• Catalysis, kinetics and reactors • Previous Articles     Next Articles

CH4 formation and C—C coupling mechanism on (011) surface of η-Fe2C Fischer-Tropsch catalyst

Nan SONG(),Minjian PAN,Bingxu CHEN,Gang QIAN,Xuezhi DUAN(),Xinggui ZHOU   

  1. State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China
  • Received:2019-01-21 Revised:2019-04-04 Online:2019-07-05 Published:2019-07-05
  • Contact: Xuezhi DUAN

费托催化剂η-Fe2C (011)上CH4形成及C-C耦合机理研究

宋楠(),潘敏建,陈炳旭,钱刚,段学志(),周兴贵   

  1. 华东理工大学化学工程联合国家重点实验室,上海 200237
  • 通讯作者: 段学志
  • 作者简介:宋楠(1983—),女,博士研究生,讲师,<email>cuiky@ecust.edu.cn</email>
  • 基金资助:
    国家自然科学基金面上项目(21776077);上海市自然科学基金面上项目(17ZR1407300)

Abstract:

Fe2C is the main active phase of low temperature Fe-based Fischer-Tropsch catalysts. It is of great significance to study the mechanism of Fischer-Tropsch reaction. Herein, spin-polarized density functional theory(DFT) calculations are performed to investigate the mechanism of CH4 formation and C—C coupling on the η-Fe2C(011) surface, where this crystal phase is thermodynamically stable. The calculated results show that the effective barrier of CH4 formation on such surface is 1.03 eV, lower than those of C—C coupling, and the C + CH3 is the most likely C—C coupling pathways. Subsequently, the effective barrier difference between the CH4 formation and C1—C1 coupling is used as a descriptor to compare the difference of the Ficher-Tropsch synthesis (FTS) selectivity between the η-Fe2C(011) surface and other Fe-based catalysts surfaces. The FTS selectivity is found to be highly sensitive to the crystal phases and surfaces of Fe-based catalysts, and the η-Fe2C(011) surface shows relatively high CH4 selectivity.

Key words: DFT calculations, Fischer-Tropsch synthesis, η-Fe2C catalyst, methane formation, C—C coupling

摘要:

Fe2C是低温Fe基费托催化剂的主要活性相,研究其上费托反应机理具有十分重要的意义。从原子尺度上通过密度泛函理论(DFT)计算研究了Fe2C稳定晶相η-Fe2C的(011)表面上甲烷形成和C—C耦合的反应机理。计算结果表明,η-Fe2C(011)表面上甲烷形成的有效能垒为1.03 eV,其低于CHi+CHj耦合反应的有效能垒(1.52~2.98 eV),且最可能的C—C耦合反应路径为C+CH3。进一步比较研究了η-Fe2C(011)表面与其他Fe基费托催化剂表面之间的CH4和C2+选择性差异,发现选择性高度敏感于Fe基催化剂的表面与体相结构,其中η-Fe2C(011)表面具有较高的甲烷选择性。

关键词: DFT计算, 费托合成, η-Fe2C催化剂, 甲烷形成, C—C耦合

CLC Number: